Method for maintaining high level of activity for supported manganese oxide acceptors for hydrogen sulfide



Filed Oct;

- NET 1 GAS J. D. BATCHELOR ETAL METHOD FOR MAINTAINING HIGH LEVEL OFACTIVITY FOR SUPPORTED MANGANESE OXIDE ACCEPTORS OR HYDROGEN SULF'IDE28, 1957 2 Sheets-Sheet 1 HIGH SULFUR CARBONACEOUS FLUE GAS souos AND soA ll 2O REGENERATED l4-\ l2 ACCEPTOR V DESULFURIZATION REGENERATION .rlOrl8 3f 7 SULFIDED ACCEPTOR LOW SULFUR AIR CARBONACEOUS SOLIDS FIG. I

FIG. 3

INVENTORS JAMES D. BATCHELOR GEORGE P. CURRAN EVERETT GORIN AT T0 RNEY1960 J. D. BATCHELOR ET AL 2,950,229

METHOD FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESEOXIDE ACCEPTORS FOR HYDROGEN SULFIDE Filed Oct. 28, 1957' 2 Sheets-Shet2 REACTIVATED, REGENERATED 1 ACCEPTOR HIGH SULFUR NET CARBONACEOUS FLUEGAS GAS souos AND so T' 4 REGENERATED Y Q 2\ /{|2ACCEPT0RDESULFURIZATION REGENERATION MPG) FIFO-(OM50 I6 I? SU LFIDED g '9 QACCEPTOR 1 LOW SULFUR AIR CARBONACEOUS souos T 1 2| {/33 l FIRST 2sSTAGE REACTIVATION VESSEL I l 1 3| 30 T SECOND AIR 22) r STAGE R AREACTIVATION E c VESSEL E T g X o T R 5 32 29 29 GAS 7 v v f I INVENTORSJAMES D. BATCHELOR GEORGE F! CURRAN EVERETT GORIN ATTORNEY United StatesPatent METHOD FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTEDMANGANESE OXIDE ACCEPTORS FOR HYDROGEN SULFIDE James D. Batchelor,Bethel Park, and George P. Curran and Everett Gorin, Pittsburgh, Pa.,assignors to Consolidation Coal Company, Pittsburgh, Pa., a corporationof Pennsylvania Filed Oct. 28, 19 57, Ser. No. 692,897

12 Claims. (Cl. 202-31) The .present invention relates to a process formaintaining a high state of activity in supported manganese oxideacceptors for hydrogen sulfide. More particularly, it relates to aprocess for removing sulfur contamination from carbonaceous solidmaterials by treatment with hydrogen in the presence of manganeseoxide-type solid acceptors for hydrogen sulfide.

Such sulfur removal processes for carbonaceous solid fuels have beendescribed in copending U.S. patent application S.N. 527,705, now U.S.Patent 2,824,047, filed August 11, 1955, by Everett Gorin, George P.Curran and James D. Batchelor, assigned to the assignee of the presentinvention. A further process relating to sulfur removal and calcining ofcarbonaceous solid fuel briquets has been described in copending U.S.patent application S.N. 635,278, filed January 22, 1957, and sinceabancloned, and in copending U.S. patent application S.N. 1,837, filedJanuary 5, 1960, both by James D. Batchelor, Everett Gorin, George P.Curran and Robert J. Friedrich, both assigned to the assignee of thepresent invention.

The presence of sulfur in carbonaceous solid fuels limits their use inmetallurgical applications. Accordingly, most metallurgical fuels areobtained by employing low sulfur content starting materials, e.g., lowsulfur coal is convcrtedto low sulfur metallurgical coke. Sulfur removalprocesses of the type described in the aforementioned patentapplications permit the use of high sulfur content fuels as startingmaterials for preparing low sulfur content carbonaceous fuels formetallurgical use. For example, the sulfur removal process may beprovided as a treatment for the solid residue (termed char) resultingfrom low temperature carbonization of bituminous coal. Where fluidizedlow temperature carbonization processes are used, the finely divided,low density, porous char product is particularly amenable to thosedesulfurization treatments. The desulfurization presence of hydrogen anda solid acceptor for hydrogen sulfide. A preferred acceptor in thisprocess is one containing manganese oxide impregnated on an inert support.

According to that process, carbonaceous solid fuels containing sulfurare mixed with a solid material (termed an acceptor) which is capable ofabsorbing hydrogen sulfide. The mixture is treated with hydrogen gas ata temperature above about 1100 F. whereby the hydrogen gas combines withthe contaminating sulfur to form 7 hydrogen sulfide; the hydrogensulfide is absorbed in situ treatment can be applied to any non-cakingcarbonaceous acceptor solids; any sulfur transferred from thecarbonaceous fuels to the bound acceptor solids would remain in thesolid coke. The processes, however, are applicable to thedesulfurization of carbonaceous briquets which may contain caking coalinter alia provided the thermal treatment is conducted to avoid severecaking and accompanying formation of large coke masses.

In the aforementioned copending application S.N. 527,705 solidcarbonized carbonaceous fuels are desulfurized by treatment at elevatedtemperatures in the by the acceptor. Since the hydrogen sulfide isabsorbed almost instantly upon formation, there is only a negligiblepartial pressure of hydrogen sulfide in the desulfurization zone forinhibiting the reactions whereby sulfur is removed from the carbonaceoussolid fuels. The reaction mixture of solids is separated into (a)product desulfurized carbonaceous solid fuels and (b) the solid acceptorcontaining accepted sulfur. The acceptor may be regenerated and heatedby contact with air to restore its hydrogen sulfide acceptor propertiesthrough elimination of previously absorbed sulfur. The heatedregenerated acceptor, when mixed with relatively cool carbonaceous solidfuels preferably provides the heat necessary to raise the solidsreaction mixture to a desulfurization temperature.

Where the sulfur-containing carbonaceous solid fuel is in the form offinely divided particles (e.g., fluidized low temperature carbonizationchar, petroleum coke and the like), the acceptor preferably is larger insize to facilitate separation of desulfurized fuel from the sulfidedacceptor. When the sulfur-containing carbonaceous solid fuel is in theform of relatively large agglomerate masses, such as briquets, theacceptor preferably is in the form of finely divided fiuidizable sizeparticles to improve contacting etficiency and to facilitate separationof desulfurized fuel from the sulfided acceptor.

Carbonaceous solid fuels contain sulfur in at least three forms. Some ofthe sulfur exists as readily removable sulfur which is organically boundin the carbonaceous fuel. This organically bound sulfur can be removedfrom the carbonaceous solid fuels rather easily by contact withhydrogen. If the readily removable, organically bound sulfur isrepresented as &S, the desulfurization reaction may be represented asfollows:

Some of the sulfur exists as inorganically bound sulfur usually in theform of metallic (principally iron) sulfide. This sulfur may be removedrather readily by treating the carbonaceous solid fuel with purehydrogen gas. The reaction (assuming iron sulfide) is as follows:

librium value. Thus in order to remove inorganically bound sulfureffectively, the ratio of must be maintained at an extremely low value,i.e.,

nearly pure hydrogen must be used.

A further type of sulfur existing in the solid carbonaceous fuels isidentified as difiicultly removable sulfur which is principallyorganically bound. This type of sulfur exists in the form of refractoryorganic material and various inorganic sulfides. While this sulfurtheoretically can be removed by treatment of the carbonaceous 'solidfuels with pure hydrogen gas, nevertheless, even 'minute traces ofhydrogen sulfide are sufficient to inhibit the transfer of sulfur fromthe solids to the gas. Removal of the difliculty removable sulfur is notpracticable under feasible processing conditions.

The ultimate desulfurization which can be achieved at any temperaturedepends upon the ratio of ms H2 in the treating gases without regard tothe absolute pressure of the reaction system. While greater absolutepressure increases the rate of desulfurization, it does not affect theultimate level of sulfur in the treated solids. In accordance with thesefindings, satisfactory desulfurization rates may be achieved attemperatures above about 1100" F. with atmospheric pressure. Higherpressure accomplishes the same desulfurization in shorter time. Apreferred pressure range for the desulfurization is about 1 to 6atmospheres absolute.

It is possible to maintain a low value for the ratio by employingenormous quantities of hydrogen as a treating gas. For example, the useof 1000 molar volumes of pure hydrogen gas in removing one mol of sulfurwould create an environment containing 0.10 volume percent of H 8 in HAlternatively, the ratio may be maintained at a low value by removingthe H 8 from the vapor state as quickly as it is formed. The removal ofH 8 from the vapor state can be accomplished by providing in adesulfurization zone a solid acceptor which has a greater afiinity forhydrogen sulfide than those materials with which the sulfur is bound inthe carbonaceous solid fuels. A preferred solid acceptor is onecontaining manganese oxide, impregnated on an inert carrier. Suitablecarrier materials include silica, alumina and silica-alumina preferablyin the form of mullite (containing 75 to 85 percent alumina and thebalance silica).

Acceptors containing manganese oxide are preferably prepared by soakingthe inert carrier particles in an aqueous solution of a solublemanganese salt which thermally decomposes to leave a residue ofmanganese oxide. Manganese nitrate is a preferred soluble salt for thispurpose. The concentration of, the aqueous solution should be sufiicientto deposit up to about percent by weight of manganese on the carrier.The soaked carrier thereafter is heated to achieve dehydration anddecomposition of the deposited manganese salt to the manganese oxideresidue. The resulting acceptor should contain up to about 10 percent byweight of manganese, preferably from about 4 to about 8 percent.

Throughout the specification, the term manganese oxide refers tocompounds containing manganese and oxygen, such as MnO, Mn O Mn O MnOwhich compounds are principally in the form of MnO. The term higheroxides of manganese refers to compounds containing more than one atom ofoxygen per atom of manganese, e.g., Mn O Mn O MnO The reaction of themanganese oxide in the desulfurization treatment is as follows:

Thus the manganese oxide combines with the generated hydrogen sulfide toform manganese sulfide thereby re- 4 moving from the vapor phase thehydrogen sulfide formed by desulfurization of the carbonaceous solidfuel.

Following sufficient desulfurizing treatment of the carbonaceous solidfuels, the desulfurized fuels are separated from the solid acceptor andrecovered as a low sulfur carbonaceous fuel product. As such, the lowsulfur carbonaceous solid fuels are suitable for use as metallurgicalfuels.

The separated sulfided acceptor is regenerated by treatment with air torestore the manganese oxide for reuse as follows:

Thus in the overall process, the sulfur removed from the carbonaceoussolid fuels is rejected from the system in the form of sulfur dioxide.So much of the process has been more fully described in theaforementioned application, S.N. 527,705.

The use of H 8 acceptors has been briefly described in relation todesulfurization processes for carbonaceous solid fuels. Such H 8acceptors also can be used for removing H S from any gas stream,regardless of source. For example, elimination of H 8 from petroleumrefinery gases, pipeline gas, and the like can be accomplished bypassing the gases over an I-hS-acceptor containing manganese oxide. TheH 8 will be absorbed by the acceptor and the manganese oxide convertedto manganese sulfide. The sulfided acceptor can be regenerated bytreatment with air to release sulfur dioxide and restore the manganeseoxide.

The phrase H s-absorbing conditions as employed in this specificationrefers to a non-oxidizing environment containing H 8 at temperatureswhere a favorable equilibrium exists for the reaction M Mns Thepreferred temperature range for H s-absorbing conditions is about 1100to 1600 F. The ability of an acceptor to react with H 8 under HS-absorbing conditions is an important determinant in the efficiency ofthe fundamental desulfurization process.

We have found that repeated use of solid acceptors containing manganeseoxide impregnated on silica, alumina or silica-alumina carriers resultsin deactivation of of the acceptor. A brief discussion will explain thedeactivation phenomenon.

Freshly impregnated acceptor solids will remove hydrogen sulfide gasfrom a vapor stream in intimate contact therewith at a determinablerate. Subsequent regeneration of the acceptor by reaction with air willrestore the manganese oxide. However the regeneration necessarily isconducted at elevated temperatures which bring about the deactivation ofthe acceptor (under H 8- absorbing conditions). When the regeneratedmanganese oxide acceptor is employed to remove hydrogen sulfide from agas in contact therewith, a lower reaction rate will be observed.Repeated processing of the acceptor through the sulfiding andregenerating processes will result in further deactivation, i.e., acontinued lowering in the rate at which the manganese oxide will removehydrogen sulfide from a gas in contact therewith.

While the regenerated acceptor does not suffer a significant loss in itscapacity to absorb hydrogen sulfide, there is nevertheless a lowering inthe rate at which the absorption of hydrogen sulfide occurs. Hence adistinction is made between (a) The capacity of a regenerated acceptorto absorb hydrogen sulfide and (b) The rate at which a regeneratedacceptor will absorb hydrogen sulfide.

The capacity for hydrogen sulfide absorption depends upon the quantityof manganese oxide present, whereas the rate at which hydrogen sulfidecan be absorbed depends upon a condition which is referred to herein asthe acceptors activity under H S-absorbing conditions.

activity and the term reactivation refers to an increasing of thisactivity.

.Note that it is possible to have a fully regenerated ac-- ceptor (onein which all of the manganese sulfide has been converted to manganeseoxide) although that acceptor is deactivated, i.e., the regeneratedacceptor will absorb H S only at a diminished rate. Should such aregenerated (deactivated) acceptor be exposed to H S- absorbingconditions for a sufficiently long period of time, the quantity of H 8absorbed by it would depend solely on the quantity of manganese oxidewhich it contains. A reactivated, regenerated acceptor, on the otherhand, would absorb the same quantity of H in a shorter period of time.

It is believed that this deactivation of manganese oxide impregnatedcarriers results from a physical migration of the manganese into thecarrier itself. The penetration of the manganese into the carrier maysometimes be accompanied by chemical reaction resulting in the formationof manganese silicates and aluminates. Any manganese thus converted isremoved from the cyclic MnO-MnS-MnO-MnS et cetera reactions.

The principal object of the present invention is to provide a processfor reactivating a manganese impregnated acceptor which has beendeactivated. A further object is to provide a regeneration process forconverting the manganese sulfide of a manganese impregnated acceptor tothe desired manganese oxide with minimum deactivation of the acceptor. Astill further object is to provide a desulfurization process whichemploys manganese impregnated acceptors which can be recirculatedthroughout the process through sequential sulfur absorbing and sulfurelimination without severe loss of activity (under H s-absorbingconditions).

According to the present invention, a portion of recirculating sulfidedacceptor is regenerated and reactivated independently of the portion ofrecirculating sulfided acceptor. That portion which is' both regeneratedand reactivated is intimately contacted with an overwhelming excess ofoxygen at a temperature of 1000 to 1600" F. to convert substantially allof the manganese in that minor portion to higher oxide forms such as MnO and M11203.

When subsequently reduced to the MnO form, the acceptor possesses anincreased activity (under H 8- absorbing conditions). subjected to theextensive oxidation preferably is thereafter reduced substantially toMnO before re-entering the recirculating acceptor stream. We prefer toreduce the reactivated acceptor in a second reactivation treatment bytransferring the excess oxygen to a portion of sulfided acceptor alsowithdrawn from the recirculating acceptor stream From the equations, itis seen that only a relatively small quantity of the sulfided acceptoris required to effect the desired transfer of excess oxygen.

Manganese oxide exists in nature in the form of MnO; inter alia. It ispossible to reduce the MnO to lower oxides as follows:

The complete reduction train is not reversible since the i 6 thepresence of excess air, the following reactions proceed simultaneously.

diate during the oxidation, but it is quickly decomposed autogenously tothe oxide:

MnS+2O MnSO MnO+SO /:O Thus substantially all of the sulfur contained inthe acceptor is eliminated during the first stage reactivation Theacceptor which has been MnO form cannot be restored through ordinaryoxidation alone. However, it is possible through oxidation alone toreverse the reaction as follows:

For the purpose of the present invention, it is sufliphenomenon. Thesulfided acceptor contains essentially .MnS and MnO prior to thereactivation treatment. In

treatment so that the treatment provides full regeneration. In addition,the formation of higher oxides of manganese accomplish a reactivation ofthe acceptor (under H S-absorbing conditions). While the describedreactivation treatment does not fully restore the activity (under Pis-absorbing conditions) of the regenerated acceptor, nevertheless, asignificant increase in activity is achieved. Maximum activity is notrequired in most carbon desulfurization processes since an overwhelmingexcess of acceptor is employed in order to supply the heat required inthe desulfurization zone.

Normallyfa small quantity of carbonaceous material will be commingledwith the sulfided acceptor recovered from the desulfurization zone. Thiscarbonaceous material will be transferred from the desulfurization zoneto the reactivation zone to supply the heat requirements via combustion.

For a full understanding of the present invention, its objects andadvantages, reference should be had to the following detaileddescription and accompanying drawings in which:

Figure 1 is a schematic flow diagram illustrating a desulfurizationprocess for carbonaceous solid fuels employing solid acceptors forhydrogen sulfide;

Figure 2 is a schematic flow diagram illustrating the reactivationprocess steps embodied in the present invention; and

Figure 3 is a graphical representation of the activity loss formanganese oxidetype acceptors according to length of exposure toelevated temperatures.

The generalized flow sheet of Figure 1 illustrates the manner in whichan acceptor desulfurization process can be carried out in a continuousmanner. A desulfurization zone 10 receives noncaking carbonaceous solidscontaining sulfur through a conduit 11 and regenerated acceptor solidsthrough a conduit 12. In this instance, the active ingredient of theacceptor solids is manganese oxide. A hydrogen-rich treating gasconsisting essentially of hydrogen is introduced into thedesulfurization zone 10 through a conduit 13. Additional gases,consisting of hydrogen gas, are autogenously produced throughdevolatilization of the carbonaceous solids at the elevated temperatureof the desulfurization zone 10. Under preferred operating conditions theautogenously produced devolatilization gases will be in suflicientquantity to provide the full hydrogen requirements for desulfurizationso that extrinsic hydrogen production is not required.

The desulfurization zone 10 is maintained at a temperature from about1100 to about 1600 F. Below about 1100 F., the desulfurization rate islow. Operation above about 1600 F. requires excessive heat and alsopromotes rapid deactivation of the acceptor. The pressure levelpreferably is high enough to provide a hydrogen gas partial pressure ofat least one atmosphere. A total pressure of from one to six atmospheresis preferred.

A typical char (containing sulfur) produced by fluidized carbonizationof Pittsburgh Seam coal at 950 F. yields devolatilization gasescontaining 58.6 percent hydrogen and 24.8 percent methane at 1.3atmospheres and 1350 F. The same char yields devolatilization gasescontain- 7 ing 48.7 percent hydrogen and 32.9 percent methane at 3atmospheres and 1350 F.

During passage through the desulfurization zone 10, the treating gasesremove sulfur from the carbonaceous solid fuels forming hydrogensulfide.

The H 8, upon formation, is at once absorbed by the solid acceptor andremoved from the gas phase.

Gases are recovered from the desulfurization zone 10 through a conduit14 and recirculated through conduit 16 for further contact withcarbonaceous solids undergoing desulfurization. A net product gas isremoved through a conduit 15.

The required residence of carbonaceous solids in the desulfurizationzone 10 depends upon the lability of the contaminating sulfur and alsoupon the level of desulfurization desired. It must be borne in mind thatthe ultimate sulfur level of the product is determined by the level of HS concentration which the manganese oxide will maintain. Where thehydrogen partial pressure of the treating gases is about one atmosphereor greater, satisfactory desulfurization can be achieved by subjectingthe carbonaceous solids to the desulfurization conditions for a periodof about three hours or less. Increased absolute pressure, as alreadypointed out, promotes more rapid desulfurization.

Desulfurized carbonaceous solids are removed from the desulfurizationzone 10 as product through a conduit 16.

Sulfided acceptor is removed through a conduit 17 and The temperaturewithin the regeneration zone 18 is maintained at about 1300 to 1600 F.Hot flue gases containing sulfur dioxide are removed from theregeneration zone 18 through a conduit 20.

Excessive oxidation in the regeneration zone 18 should be avoided inorder to restrict the quantity of higher oxides of manganese produced.Ideally, some of the acceptor solids recovered from the regenerationzone 18 should be in the form of MnS. By maintaining from about 2 toabout 15 percent of the manganese as MnS after regeneration, the oxidesof manganese can be m aintained principally in the form of MnO ratherthan as higher oxides such as Mn O or Mn O The presence of higher oxidesof manganese in the desulfurization zone undesirably consumes hydrogengas without accompanying sulfur removal as will be hereinafterdescribed. In general, the amount of oxygen used in the regenerationzone 18 should be within about 20 percent of the stoichiometricquantity, which would be required for oxidizing all of the MnS to MnOaccording to the equation above.

Regenerated acceptor is returned to the desulfurization zone 10 throughthe conduit 12 without deliberate cooling to serve therein as a meansfor removing H therefrom and to supply the heat requirements thereof.

When the desulfurization process is operated as described with anacceptor comprising manganese oxide impregnated on an inert carrier,deactivation of the acceptor will occur as a result of its thermalexposure. According to the present process as illustrated in Figure 2,the acceptor deactivation may be retarded. In Figure 2, the elements ofthe process relating to the desulfurization stage bear numeralscorresponding to those of Figure 1. Corresponding numerals identifycorresponding elements. Regenerated acceptor solids are introduced intothe desulfurization stage through a conduit 12.

Sulfided acceptor solids comprising inert carriers containing manganesesulfide and manganese oxide are recovered from the desulfurization stage10 through a conduit 17. A :portion of the sulfided'acceptor isregenerated in the usual manner by treatment with air at about 1300 to1600 F. in the regeneration zone 18. Another portion of therecirculating sulfided acceptor is withdrawn through the conduit 21 andtransported as a suspension in air (from a conduit '22) through aconduit 23 into a first reactivation vessel 24. The acceptor ismaintained in intimate contact with oxygen within the reactivationvessel 24 preferably in the fluidized state with air as a fiuidizinggas. The first reactivation vessel 24 is maintained at a temperature of1000 to 1600 F. The pressure is preferably that maintained in thedesulfun'zation zone 10. The acceptor solids remain in the firstreactivation vessel 24 for a sufiicient period, from about 5 minutes toseveral hours, to achieve substantially complete conversion of all themanganese to a higher oxide form. Any manganese sulfide entering thefirst reactivation vessel 24 will be converted into an oxide ofmanganese and will form sulfur dioxide. The spent gases, includingsulfur dioxide and oxygen-depleted fiuidizing gas, are removed through aconduit 25. Usually sufiicient carbonaceous fuel will be commingled withthe recirculating sulfided acceptor to provide the heat requirements ofthe first reactivation vessel 24 via combustion in the oxidizingenvironment therein.

A substantial excess of oxygen is supplied to the first reactivationvessel 24 over that determined by the stoichiometry of the reaction.

Preferably an oxygen excess from about five-fold to about fifty-fold isprovided to assure maximum oxidation of the manganese of the acceptor.

The quantity of acceptor subjected to the reactivation treatment of thisinvention is quite small in relation to the total recirculating streamof sulfided acceptor. In general, from about 1 to about 10 percent ofthe sulfided acceptor recovered from the desulfurization zone 10 will bereactivated. The major portion of sulfided acceptor recovered from thedesulfurization zone 10, preferably more than percent, will beregenerated in the regeneration zone 18 as already described.

The regenerated, reactivated acceptor solids are withdrawn from thefirst reactivation vessel 24 principally as higher oxides of manganesethrough a conduit 26 for reuse in the process. The reactivated,regenerated acceptor solids from conduit 26 may be introduced into theconduit 12 (containing the major portion of regenerated acceptor solids)for reintroduction into the recirculating stream of acceptor solids.This procedure is undesirable since the higher oxides of manganese areimmediately reduced .to MnO on entry into the hydrogen-rich environmentwithin the desulfurization zone 10:

M11304 +H:- 3 MnO M1120 H2) Consumption of valuable hydrogen gas in thismanner is inefficient since there is no accompanying desulfurization.Moreover, the reduction of these higher oxides generates water vaporwhich has a tendency to suppress the fundamental H s-absorbing reaction:

The equilibrium for the H s-absorbing reaction is a function of PHQO Thereducing treatment is carried out in a second reactivation vessel 30.

Accordingly, the reactivated acceptor containing higher oxides ofmanganese is withdrawn from conduit 26 through a conduit 27. Astoichiometric quantity of sulfided acceptor containing manganesesulfide is withdrawn from the conduit 17 through a conduit 28. Bothacceptor streams are joined and introduced through a conduit 29 into areaction vessel 30. A gas, preferably nonoxidizing, is introduced intothe vessel 30 through the conduit 29 to fluidize the bed of acceptortherein and provide intimate contacting conditions. The fiuidizing gasshould be free of sulfur compounds. Air may be used for this purpose,although an inert flue gas is preferred. Within the second reactivationvessel 30, the reactivated acceptor is reduced and the sulfided acceptoris regenerated as described.

Spent fluidizing gas containingSO is removed from the secondreactivation vessel 30 through a conduit 31. The reaction between MnSand higher oxides of manganese is quiterapid, indicating the greataffinity of MnS for reacting with oxygen. A residence time of theacceptor within the second reactivation vessel 30 of from a few minutesto several hours is satisfactory. Thus treated acceptor, principally asMnO, is withdrawn from the second reactivation vessel 30 through aconduit 32. In its reactivated, regenerated form, the acceptor fromconduit 32 may be introduced directly into the desulfurization zone 10through the conduit 12. The second reactivation vessel 30 is preferablymaintained at a tem perature of about 1300 to 1700 F.

The relative quantities of reactivated acceptor and sulfided acceptorinteracting in the second reactivation vessel 30 can be calculated fromthe following generalized equation in which X refers to the ratio ofoxide-form oxygen to manganese in the acceptor:

3 T X +2 X MnO MnO-l- S Alternatively, the second reactivation vessel 30may be eliminated and the reactivated acceptor may be reduced directlyin the regeneration vessel 18. According to this alternative embodiment,the reactivated acceptor (containing higher oxides of manganese) isrecovered from the first reactivation vessel 24 through the conduit 26and transferred directly to the regeneration zone 18 through a conduit33. Interaction between the sulfided of the acceptor is placed in acontainer adapted to confine the acceptor in a bed under fluidizingconditions. A stream of gas having a predetermined composition ofhydrogen and H 8 is passed upwardly through the bed of acceptor at apredetermined constant rate as a fluidizing gas. Usually the gascontains about 0.7 percent H 8 in hydrogen. The fraction of entering H Swhich reacts with the acceptor is measured. Initially substantially allof the entering H S reacts with the acceptor.

For each mol of H 8 reacted, one mol of water is formed. Thus the amountof water in the eflluent gas is a direct measure of the H 8 reaction.

grams of H 8 reacted per hour grams of unreacted MnO in the acceptor bedA freshly prepared acceptor has an activity which can be expressed asunity. The measured activity of any other acceptor under investigationcan be compared with that of the freshly prepared acceptor (expressed asunity).

To develop the curves of Figure 3, a mullite carrier impregnated withmanganese oxide was used. The carrier contained 4 percent of manganese.Samples of the acceptor were exposed to elevated temperatures forvarying periods of time to illustrate the efiect of thermal exposure onactivity loss. The activity of each sample was determined and comparedwith that of a freshly prepared acceptor. The activity values (expressedas a percentage of the fresh acceptor activity) are presentedgraphically in Figure 3 for each temperature level of thermal exposure.

The time required for a 50 percent loss in activity would be about 5hours at 1600 F., about 6 hours at 1500 F., about 87 hours at l400 F.and about 210 hours at 1350" F. Since the desulfurization processes areoperated with an overwhelming excess of acceptor material, maintenanceof a maximum activity level is not requisite. Accordingly, fullrestoration of activity is not required during each regeneration cycle.Thus only a small portion of the recirculating stream of acceptor issubjected to the reactivating treatment of the present invention. Forexample, from about 1 to '10 percent by weight of the acceptor solidsundergoing regeneration would be exposed to the reactivation treatmentof this invention.

To illustrate the eflicacy of reactivation of the present process, anacceptor was selected comprising a mullite carrier containing 4.02percent by weight of manganese. By virtue of extensive thermaltreatment, this acceptor had an activity (under H S-absorbingconditions) only 45 percent of its original activity (under Hs-absorbing conditions). About 94 percent of the manganese in theacceptor was in the form of manganese sulfide.

Example 1.-To illustrate efi'icacy of first reactivation stage Thedeactivated sulfided acceptor was maintained in a fluidized state at1000 F. for two hours by passing oxygen gas upwardly therethrough at apartial pressure of one atmosphere oxygen. The acceptor thereaftercontained manganese substantially entirely as Mn O This acceptor wasreduced in a hydrogen atmosphere at 1350 F. to restore the manganese tothe MnO form. The reduced, reactivated acceptor thereafter had anactivity (under H s-absorbing conditions) about 73 percent of itsoriginal activity (when freshly prepared).

Example 2.-T 0 illustrate efiicacy of second reactivation stage Anacceptor containing manganese oxide was reactivated via the describedoxidation to a composition MnO indicating the presence of higher oxidesof manganese, and simulating the reactivated acceptor in the conduit 26.A sulfided acceptor was obtained in where X had a value of 1.265. Theresulting acceptor mixture contained manganese substantially entirely asMnO.

According to the provisions of the patent statutes, we have explainedthe principle, preferred construction, and mode of operation of ourinvention and have illustrated and described what We now consider torepresent its best embodiment. However, we desire to have it understoodthat, within the scope of the appended claims, the invention may bepracticed otherwise than as specifically illustrated and described.

We claim:

1. In a process employing solid acceptors for hydrogen sulfidecomprising manganese oxide impregnated'on an inert support for absorbinghydrogen sulfide at temperatures above about =1 100 F. to form manganesesulfide, followed by oxidizing the manganese sulfide to manganese oxideby reaction with oxygen at elevated temperatures above about 1300 F.,wherein the acceptors suffer a decrease in H S-absorbing activityfollowing said oxidizing, the improvement which minimizes lms of theacceptors activity under H s-absorbing conditions, comprising intimatelycontacting a minor portion of the manganese sulfide-containing sulfidedacceptors with excess oxygen at a temperature of 1000 to 1600" F.,converting thereby substantially all of the contacted manganese sulfideto higher oxides of manganese and thereafter recovering the thus-treatedacceptors containing higher oxides of manganese reducible to manganeseoxide having an increased H S-absorbing activity.

2. The improvement of claim 1 wherein the inert support is selected fromthe class consisting of silica, alumina and silica-alumina.

3. The improvement of claim 1 wherein the inert support is mullite. 4.In a process employing solid acceptors for hydrogen sulfide comprisingmanganese oxide impregnated on an inert support for absorbing hydrogensulfide at temperatures above about 1100 F. to form manganese sulfide,followed by oxidizing the manganese sulfide to manganese oxide byreaction with oxygen at elevated temperatures above about 1300 F.,wherein the acceptors suffer a decrease in H S-absorbing activityfollowing said oxidizing, the improvement which minimizes loss of theacceptors activity under fi s-absorbing conditions, comprisingintimately contacting a major portion of the sulfided acceptors withoxygen at a temperature of 1300 to 1600" F. to convert substantially allof the contacted manganese sulfide to manganese oxide, contacting aminor portion of the manganese sulfide-containing sulfided acceptorswith excess oxygen at a temperature of 1000 to 1600 F., convertingthereby substantially all of the thus-contacted manganese sulfide tohigher oxides of manganese, thereafter recovering the thus-treated minorportion containing higher oxides of manganese reducible to manganeseoxide having an increased H S-absorbing activity and recombining withsaid ma or portion.

5. In a process employing solid acceptors for hydrogen sulfidecomprising manganese oxide impregnated on an inert support for absorbinghydrogen sulfide at temperatures above about 1100 F. to form manganesesulfide, followed by oxidizing the manganese sulfide to manganese oxideby reaction with oxygen at elevated temperatures above about 1300" F.,wherein the acceptors suffer a decrease in H S-absorbing activityfollowing said oxidizing, the improvement which minimizes loss of theacceptors activity under H S-absorbing conditions, comprising intimatelycontacting a major portion of the sulfided acceptors with oxygen at atemperature of 1300 to 1600 F. to convert substantially all of thecontacted manganese sulfide to manganese oxide, contacting a first minorportion of the manganese sulfide- -containing sulfided acceptors withexcess oxygen at a temperature of 1000 to 1600" F., converting therebysubstantially all of the thus-contacted manganese sulfide to higheroxides of manganese, thereafter contacting a second minor portion of thesulfided acceptors with the thus-treated first minor portion at atemperature of 1300 to 1700 F. whereby the manganese sulfide of saidsecond minor portion is converted to manganese oxide by reaction withoxygen released from said first minor portion whose higher oxides ofmanganese are converted substantially to manganese oxide, recovering thethustreated first and second minor portions containing manganese oxidehaving an increased H S-absorbing activity and recombining with saidmajor portion.

6. In the method of removing sulfur from particulate carbonizedcarbonaceous solids, which comprises preparing an intimate admixture ofsaid carbonaceous solids and particulate acceptor solids comprisinginert carriers having manganese oxide impregnated thereon, subjectingsaid admixture to treatment at a temperature above .1100 F. in thepresence of hydrogen gas until a portion of the initial sulfur has beenremoved from said carbonaceous solids and transferred to said acceptorsolids forming manganese sulfide, separating particulate acceptor solidscontaining manganese sulfide from low sulfur carbonaceous solids,recovering low sulfur particulate carbonaceous solids as product, andrestoring the H s-absorbing property of sulfided acceptor solids forrecirculation in the process, the improvement in the lastmentioned stepcomprising contacting a major portion of said sulfided acceptor solidsat a temperature of 1300 to 1600 F. under oxidative conditions to removesulfide sulfur therefrom and reform man anese oxide thereby, contactinga minor portion of said sulfided acceptor solids at a temperature of1000 to 1600 F. with excess oxygen to convert substantially all of themanganese sulfide to higher oxides of manganese, thereafter reducing thehigher oxides of manganese in said minor portion substantially tomanganese oxide, and recombining the thus-treated minor portion with thetreated major portion for repeated admixing and processing with saidparticulate carbonized carbonaceous solids.

7. The method of claim 6 wherein the particulate carbonized carbonaceoussolids are carbonaceous briquets and the inert carriers comprise finelydivided fluidizable size particles of an inert material selected fromthe class consisting of silica, alumina and silica-alumina.

*8. The method of claim 6 wherein the particulate carbonizedcarbonaceous solids comprise char produced by fluidized low temperaturecarbonization of caking bituminous coal.

9. In a process employing solid acceptors for hydrogen sulfidecomprising manganese oxide impregnated on an inert support for absorbinghydrogen sulfide at temperatures above about 1100 F. to form manganesesulfide, followed by oxidizing the manganese sulfide to manganese oxideby reaction with oxygen at elevated temperatures above about 1300 F.,wherein the ac- .ceptors suffer a decrease in H s-absorbing activityfolv lowing said oxidizing, the improvement which minimizes loss of theacceptors activity under H S-absorbing conditions, comprising intimatelycontacting a major portion of the sulfided acceptors with oxygen in aregeneration zone at a temperature of 1300 to 1600 F. to convertsubstantially all of the contacted manganese sulfide to manganese oxide,contacting a minor portion of the manganese sulfide-containing sulfidedacceptors with excess oxygen at a temperature of 1000 to 1600 F.,converting thereby substantially all of the thus-converted manganesesulfide to higher oxides of manganese, thereafter introducing thethus-treated minor portion into said regeneration zone to reduce saidhigher oxides of manganese substantially to manganese oxide andrecovering from said regeneration zone, in admixture with said majorportion, the minor portion containing manganese oxide having anincreased H s-absorbing activity.

10. In the method of removing sulfur from particulate carbonizedcarbonaceous solids, which comprises preparing an intimate admixture ofsaid carbonaceous solids and particulate acceptor solids comprisinginert carrier having manganese oxide impregnated thereon, subjectingsaid admixture to treatment at a temperature above 1100 F. in thepresence of hydrogen gas until a portion of the initial sulfur has beenremoved from said carbonaceous solids and transferred to said acceptorsolids forming manganese sulfide, separating particulate acceptor solidscontaining manganese sulfide from low sulfur carbonaceous solids,recovering said low sulfur particulate carbonaceous solids as product,and restoring the H s-absorbing property of sulfided acceptor solids forrecirculation in the process, the improvement in the last-mentioned stepcomprising contacting a major portion of said sulfided acceptor solidsin a regeneration zone at a temperature of 1300 to 1600? F. underoxidative conditions to remove sulfide sulfur therefrom and reformmanganese oxide thereby, contacting a minor portion of said sulfidedacceptor solids at a temperature of 1000 to 1600 F. with excess oxygento convert substantially all of the manganese sulfide to higher oxidesof manganese, thereafter introducing the thus-treated minor portion intosaid regeneration zone to reduce said higher oxides of manganese tomanganese oxide and recovering from said regeneration zone thethus-treated minor portion containing manganese oxide having anincreased H S-absorbing activity in admixture with the treated majorportion for repeated admixing and processing with such particulatecarbonized carbonaceous solids.

11. The method of claim 10 wherein the particulate carbonizedcarbonaceous solids are carbonaceous briquets and the inert carrierscomprise finely divided fluidizable size particles of an inert materialselected from the class consisting of silica, alumina andsilica-alumina.

12. The method of claim 10 wherein the particulate carbonizedcarbonaceous solids comprise char produced by fluidized low temperaturecarbonization of caking 25 bituminous coal.

References Cited in the file of this patent UNITED STATES PATENTS2,824,047 Gorin et al. Feb. 18, 1958

1. IN A PROCESS EMPLOYING SOLID ACCEPTORS FOR HYDROGEN SULFIDECOMPRISING MANGANESE OXIDE IMPRIGNATED ON AN INERT SUPPORT FOR ABSORBINGHYDROGEN SULFIDE AT TEMPERATURES ABOVE ABOUT 1100*F. TO FORM MANGANESESULFIDE, FOLLOWED BY OXIDIZING THE MANGANESE SULFIDE TO MANGANESE OXIDEBY REACTION WITH OXYGEN AT ELEVATED TEMPERATURES ABOVE ABOUT 1300*F.,WHEREIN THE ACCEPTORS SUFFER A DECREASE IN H2S-ABSORBING ACTIVITYFOLLOWING SAID OXIDIZING, THE IMPROVEMENT WHICH MINIMIZES LOSS OF THEACCEPTORS'' ACTIVITY UNDER H2S-ABSORBING CONDITIONS, COMPRISINGINTIMATELY CONTACTING A MINOR PORTION OF THE MANGANESESULFIDE-CONTAINING SULFIDED ACCEPTORS WITH EXCESS OXYGEN AT ATEMPERATURE OF 100 TO 1600*F., CONVERTING THEREBY SUBSTANTIALLY ALL OFTHE CONTACTED MANGANESE SULFIDE TO HIGHER OXIDES OF MANGANESE ANDTHEREAFTER RECOVERING THE THUS-TREATED ACCEPTORS CONTAINING HIGHEROXIDES OF MANGANESE REDUCIBLE TO MANGANESE OXIDE HAVING AN INCREASEDH2-S-ABSORBING ACTIVITY.